ByLawrence Hurley, ReutersNovember 9, 2016

The Supreme Court is seen in Washington, June 30, 2014. Donald Trump will enter the Oval Office with the ability to re-establish the Supreme Court’s conservative tilt and the chance to cement it for the long term.

WASHINGTON — Republican Donald Trump's presidential election victory all but dooms major Obama administration initiatives that are already tied up in legal challenges and gives him the chance to appoint a pivotal fifth conservative justice on the US Supreme Court.

Democratic President Obama's signature 2010 healthcare law, his plan to combat climate change, his executive action on immigration, his transgender rights policy, and other issues were challenged in court by Republicans and industry groups.

A Trump administration could decide no longer to defend the policies in court after he takes office on Jan. 20. In addition, Mr. Trump and the incoming Republican-led Congress could simply repeal or rescind Obama's policies, as they have promised.

Trump's Supreme Court appointment, possibly the first of multiple picks, would allow him to restore the decades-long conservative majority on the bench, which looked under threat when conservative Justice Antonin Scalia died in February. The shorthanded court currently is split with four conservatives and four liberals.

Conservative activists may be emboldened to bring cases urging the court to support gun rights, uphold abortion restrictions, and rule for religious rights.

"If you have a conservative court, you are going to have more conservative decisions," said Kerri Kupec, a lawyer with the Alliance Defending Freedom, a conservative Christian legal group involved in religious rights cases.

Liberal hopes of gaining a majority on the Supreme Court for the first time in decades lasted almost nine months, from Justice Scalia's death on Feb. 13 to Tuesday night.

In a vindication of Republican Senate leader Mitch McConnell's decision, with little precedent in US history, to take no action on Obama's nominee to replace Scalia, appeals court judge Merrick Garland, Trump is now poised to nominate a new justice as soon as he takes office.

His nominee would be considered for confirmation by a Republican-controlled Senate under McConnell.

Trump may also be able to make further appointments to the court, with three justices 78 or older, including 83-year-old liberal Ruth Bader Ginsburg, who Trump called on to resign in July after she called him a "faker" and speculated about the possibility of moving to New Zealand if he won the White House.

If Trump is able to replace Ginsburg or another liberal justice during his presidency, the court's conservative wing would be further strengthened.

Such a majority "could be a threat to important rights that have been protected in the past by the Supreme Court," said Elizabeth Wydra, president of the Constitutional Accountability Center, a liberal legal group. She cited abortion rights and efforts at ensuring racial equality as examples.

A conservative court, as it was with Scalia on the bench, likely would be favorable toward gun rights, skeptical of abortion, and supportive of the death penalty. If Democrat Hillary Clinton had won Tuesday's election, liberals may have been emboldened to challenge the constitutionality of the death penalty and seek gun restrictions and limits on campaign spending, among other things.

Trump's list

Trump has already issued a list of 21 judges, mainly federal judges appointed by President George W. Bush and state court judges, who he said he would consider to fill Scalia's vacancy. All have conservative credentials on such issues as abortion, birth control, and gun rights.

The case that could be affected by Trump's win soonest involves transgender rights. The court on Oct. 28 took up a case concerning a female-born transgender high school student named Gavin Grimm, who identifies as male and sued in 2015 to win the right to use the school's boys' bathroom. Gavin is backed by the Obama administration.

No date has yet been set for the argument in the case. The court could potentially delay acting until it has nine justices.

A ruling could resolve similar litigation around the country over an Obama administration directive saying schools should allow transgender students to use the bathroom of their choosing.

Trump has said he would rescind the Obama directive. He also has said he would rescind Obama's executive action to protect millions of immigrants in the country illegally from deportation and give them work permits, which was put on hold by the courts while the administration continues to fight to revive it.

Trump would be expected to overturn major regulations put in place under Obama, including the Clean Power Plan to curb greenhouse emissions mainly from coal-fired power plants. That process takes time, meaning that the Supreme Court could potentially rule on a legal challenge to the Clean Power Plan before Trump can dump it. The case is pending before an appeals court in Washington.

The Republican Congress under Trump could now seek to repeal Obama's signature healthcare law, the Affordable Care Act, but even if it does not, a Republican legal challenge that could cripple the law is pending before a federal appeals court in Washington.